Rod reducer apparatus and method for spinal corrective surgery

ABSTRACT

Spinal rod reduction apparatuses, systems, and methods are provided. In various examples, a rod reduction apparatus includes a first threaded member including an engagement feature configured to selectively anchor the first threaded member to the implantable screw assembly. A second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the implantable screw assembly with rotation of the second threaded member in a first rotational direction.

CLAIM OF PRIORITY

This Application is a divisional of U.S. patent application Ser. No. 13/139,373, filed Feb. 9, 2012, which is a National Stage of International Application No. PCT/US2009/006433, filed Dec. 8, 2009, which claims the benefit of U.S. Provisional Application No. 61/138,392, filed Dec. 17, 2008, the disclosures of all of which are incorporated herein by reference in their entireties for all purposes.

TECHNICAL FIELD

This patent document pertains generally to orthopedics. More particularly, but not by way of limitation, this patent document pertains to an apparatus and method for spinal deformity correction.

BACKGROUND

Several techniques exist in the field of spinal surgery for reducing a spinal rod into a posterior pedicle screw. The primary technique utilizes a separate rod reduction instrument that couples to the head of the screw after the screw is inserted and the rod is placed, such as rocker forks or ratchet style instruments, which are designed to reduce the rod one level at a time, i.e., to each pedicle screw separately. Such segmental reduction techniques may produce large axial loads on the pedicle screws.

Alternatively, a rod can be conformed to a specific deformity and then seated within an implanted pedicle screw. Once seated, the deformity can be corrected by bending the rod in situ. This technique may be time-consuming and places stresses and strains on the rod prior to implantation.

Certain rod reduction techniques utilize specialty reduction pedicle screws that include integrated upwardly extending tabs that can be used to reduce the rod gradually over the entire length of a deformity. Once the rod reduction is completed, the extended tabs are broken off. This technique, however, is typically limited to the reduction screw only and can cause the implant to be expensive.

Overview

The present inventors have recognized, among other things, that stresses and strains to pedicle screws and/or spinal rods present problems during spinal rod reduction procedures. The present inventors have further recognized that there exists an unmet need for a streamlined, externally mounted mini-reduction instrument that can be used on any hook or screw type, including monoaxial, polyaxial, and sagittal screws, and can be reused, modified, or removed as necessary at any time during the entire course of the spinal corrective procedure.

This patent document describes, among other things, apparatuses, systems, and methods for spinal rod reduction. In various examples, a rod reduction apparatus includes a first threaded member including an engagement feature configured to selectively anchor the first threaded member to the implantable screw assembly. A second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the implantable screw assembly with rotation of the second threaded member in a first rotational direction.

In Example 1, an apparatus is configured to selectively engage with a spinal rod and an implantable screw assembly. The apparatus comprises a first threaded member including first threads around at least a portion of an outer surface of the first threaded member. The first threaded member includes an engagement feature configured to selectively anchor the first threaded member to the implantable screw assembly. A second threaded member includes second threads around at least a portion of an inner surface of the second threaded member. The second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the implantable screw assembly with rotation of the second threaded member in a first rotational direction.

In Example 2, the apparatus of Example 1 optionally is configured such that the engagement feature includes at least one protrusion configured to mate with a corresponding number of receptacles of the implantable screw assembly.

In Example 3, the apparatus of one or more of Examples 1-2 optionally is configured such that the engagement feature includes a grasping element configured to selectively couple to a proximal end of the implantable screw assembly.

In Example 4, the apparatus of one or more of Examples 1-3 optionally is configured such that the engagement feature is disposed at a distal end of the first threaded member.

In Example 5, the apparatus of one or more of Examples 1-4 optionally is configured such that the urging member is coupled to the second threaded member.

In Example 6, the apparatus of one or more of Examples 1-5 optionally is configured such that the first threaded member is substantially tubular and includes a first leg and a second leg, the first and second legs extending substantially axially, wherein distal ends of the first and second legs are configured to be selectively radially separable.

In Example 7, the apparatus of Example 6 optionally is configured such that the first and second legs are substantially semi-circular in cross section.

In Example 8, the apparatus of Example 7 optionally is configured such that the first and second legs of the first threaded member are held together by the second threaded member threadably engaged around the outer surface of the first threaded member.

In Example 9, the apparatus of Example 8 optionally is configured such that the outer surface of the first threaded member includes a portion of decreased diameter configured to allow the first and second legs to selectively radially separate with the first threaded member threadably engaged with the second threaded member.

In Example 10, the apparatus of one or more of Examples 6-9 optionally is configured such that the first threaded member includes a gap between the first leg and the second leg, the gap being configured to accommodate the spinal rod.

In Example 11, the apparatus of Example 10 optionally is configured such that the bearing surface of the urging member is disposed at least partially within the gap between the first leg and the second leg.

In Example 12, the apparatus of one or more of Examples 1-11 optionally is configured such that the second threaded member includes a tool engagement portion configured to engage with a tool configured to rotate the second threaded member with respect to the first thread member.

In Example 13, the apparatus of Example 12 optionally is configured such that the tool engagement portion includes a recess including a drive surface configured to mate with the tool.

In Example 14, the apparatus of one or more of Examples 12-13 optionally is configured such that the tool engagement portion includes a nut configured to mate with the tool.

In Example 15, the apparatus of Example 14 optionally is configured such that the nut includes a hex nut.

In Example 16, the apparatus of one or more of Examples 1-15 optionally is configured such that the spinal rod urging member includes a claw element including one or more arms, each arm including the bearing surface configured to selectively abut the spinal rod.

In Example 17, the apparatus of Example 16 optionally is configured such that the bearing surface of each arm is disposed at an end of the arm.

In Example 18, the apparatus of one or more of Examples 16-17 optionally is configured such that the bearing surface includes a rod recess.

In Example 19, the apparatus of one or more of Examples 1-18 optionally is configured such that the engagement feature of the first threaded member includes a grasping element configured to couple to an underside of a head of the implantable screw assembly.

In Example 20, the apparatus of one or more of Examples 1-19 optionally is configured such that the second threaded member includes a gripping surface configured to grip during manual rotation of the second threaded member with respect to the first threaded member.

In Example 21, an method comprises placing at least one rod reducer along a spinal rod and substantially in alignment with at least one pedicle screw. Placement of the rod reducer along the spinal rod includes substantially aligning a bearing surface of a spinal rod urging member of the rod reducer with the spinal rod. The rod reducer is engaged with the pedicle screw. The rod reducer is incrementally actuated to gradually reduce the spinal rod into engagement with the pedicle screw. Actuation of the rod reducer causes movement of the bearing surface toward the pedicle screw to urge the spinal rod toward the pedicle screw. The pedicle screw is engaged with the spinal rod.

In Example 22, the apparatus of Example 21 optionally is configured such that engaging the pedicle screw with the spinal rod includes attaching a locking cap to the pedicle screw to retain the spinal rod in engagement with the pedicle screw.

In Example 23, the apparatus of one or more of Examples 21-22 optionally comprises removing the rod reducer from the pedicle screw after engagement of the pedicle screw with the spinal rod.

In Example 24, the apparatus of Example 23 optionally comprises cleaning the rod reducer for reuse after removal of the rod reducer from the pedicle screw.

In Example 25, the apparatus of one or more of Examples 21-24 optionally is configured such that placing the at least one rod reducer along the spinal rod includes placing two or more rod reducers along the spinal rod and substantially in alignment with two or more pedicle screws.

In Example 26, the apparatus of one or more of Examples 21-25 optionally comprises placing the spinal rod along a plurality of pedicle screws. Without using a rod reducer, the spinal rod is engaged to one or more pedicle screws for which no spinal rod reduction is necessary. Using one or more rod reducers, the spinal rod is engaged to one or more pedicle screws for which spinal rod reduction is necessary.

In Example 27, the apparatus of one or more of Examples 21-26 optionally is configured such that engaging the rod reducer with the pedicle screw includes manually engaging the rod reducer with the pedicle screw.

In Example 28, the apparatus of one or more of Examples 21-27 optionally is configured such that engaging the rod reducer with the pedicle screw includes engaging the rod reducer with the pedicle screw using a tool configured to mate with a tool engagement portion of the rod reducer.

In Example 29, a spinal rod reduction system comprises a spinal rod. A plurality of pedicle screws is configured to engage with the spinal rod. A plurality of rod reducers each includes a first threaded member including first threads around at least a portion of an outer surface of the first threaded member. The first threaded member includes an engagement feature configured to selectively anchor the first threaded member to the pedicle screw. A second threaded member includes second threads around at least a portion of an inner surface of the second threaded member. The second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the pedicle screw with rotation of the second threaded member in a first rotational direction.

In Example 30, the system of Example 29 optionally is configured such that the rod reducers are configured to engage with the pedicle screws and the spinal rod at locations where the spinal rod is spaced from the pedicle screws.

In Example 31, the system of one or more of Examples 29-30 optionally is configured such that the plurality of rod reducers are configured to incrementally urge the spinal rod toward the plurality of pedicle screws.

In Example 32, the system of one or more of Examples 29-31 optionally comprises a locking cap configured to engage with the pedicle screw and retain the spinal rod in engagement with the pedicle screw.

In Example 33, the system of one or more of Examples 29-32 optionally comprises a tool configured to mate with a tool engagement portion of each of the rod reducers, the tool being configured to rotate the second threaded member with respect to the first thread member.

In Example 34, the system of Example 33 optionally is configured such that the tool engagement portion includes a recess including a drive surface configured to mate with the tool.

In Example 35, the system of one or more of Examples 33-34 optionally is configured such that the tool engagement portion includes a nut configured to mate with the tool.

In Example 36, a spinal rod reduction assembly comprises one or more pedicle screws engaged with one or more vertebrae. A spinal rod is substantially aligned with the one or more pedicle screws. At least one rod reducer is removably engaged with at least one pedicle screw at a location where the spinal rod is spaced by a distance from the pedicle screw. The rod reducer includes a spinal rod urging member axially movable with respect to the rod reducer. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge, with actuation of the rod reducer, the spinal rod toward the pedicle screw to decrease the distance between the spinal rod and the pedicle screw.

These and other examples, advantages, and features of the present rod reduction apparatuses and methods will be set forth in part in the following Detailed Description. As such, this Overview is intended to provide an overview of subject matter of the present patent document. It is not intended to provide an exclusive or exhaustive explanation of the invention. The Detailed Description is included to provide further information about the present patent document.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like numerals describe similar components throughout the several views. Like numerals having different letter suffixes represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

FIGS. 1A and 1B illustrate a front perspective view and a front elevational view, respectively, of a miniature rod reducer instrument in accordance with an embodiment of the present document;

FIGS. 2A, 2B, and 2C illustrate a side elevational view, a cross-sectional view taken along line 2B-2B of FIG. 2A, and a top plan view, respectively, of an outer drive sleeve element of the miniature rod reducer instrument of FIG. 1;

FIGS. 3A, 3B, and 3C illustrate a front elevational view, a left side elevational view, and a top plan view, respectively, of a retaining guide ring element of the miniature rod reducer instrument of FIG. 1;

FIGS. 4A, 4B, and 4C illustrate a front elevational view, a cross-sectional view taken directly into the page of FIG. 4A, and a cross-sectional view taken along line 4C-4C of FIG. 4A, respectively, of a threaded tube element of the miniature rod reducer instrument of FIG. 1;

FIGS. 5A and 5B illustrate front perspective views of the miniature rod reducer instrument of FIG. 1 coupled to a spinal rod and a pedicle screw assembly in an unreduced and reduced rod configuration, respectively;

FIGS. 6A and 6B illustrate perspective, cross-sectional views taken along lines 6A-6A and 6B-6B of FIG. 5B of the rod reducer instrument of FIG. 1;

FIG. 7 illustrates a front perspective view of the rod reducer instrument of FIG. 1 coupled to a locking cap ratcheting T-handle driver instrument with a hex drive coupler, a spinal rod, and a pedicle screw assembly;

FIGS. 8A-8D illustrate various perspective views of a miniature rod reducer instrument in accordance with an embodiment of the present document; and

FIGS. 9A-9F illustrate various perspective views of a miniature rod reducer instrument in accordance with an embodiment of the present document.

DETAILED DESCRIPTION

The present inventors have recognized, among other things, that it is desirable to construct a streamlined, externally mounted mini-reduction instrument that can be used on any hook or screw type, including monoaxial, polyaxial, and sagittal screws, and can be reused, modified, or removed as necessary at any time during the entire course of the spinal corrective procedure.

Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” or “distally” and “outwardly” or “proximally” refer to directions toward and away from, respectively, the geometric center or orientation of the instrument assembly and related parts thereof. The words, “anterior”, “posterior”, “superior,” “inferior”, “lateral” and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import.

In reference to FIGS. 1-7, a miniature rod reducer instrument 100 in accordance with an embodiment of the present invention includes an outer drive sleeve 110, a retaining guide ring 120, and a threaded tube 130. The rod reducer 100 is selectively engageable with a spinal rod 140 and a pedicle screw assembly 150, which can assume the form of a monoaxial pedicle screw, a sagittal screw, a polyaxial pedicle screw, a hook or nearly any type of screw that includes a head or anchor seat constructed to engage a distal end of the threaded tube 130. The outer drive sleeve 110, in an example, includes a proximal end, a distal end, a longitudinal axis between the proximal and distal ends, a cannulated interior, a gripping surface 112 disposed on a proximal exterior surface that may include a knurled or other traction grip surface, a visibility window 114 that enables viewing and weight reduction, a drive surface 116 such as a hex drive disposed interior to the proximal end and a series of interior threading 118 disposed on an interior surface at the distal end. The drive surface 116, in an example, is engageable with a ratcheting T-handle driver instrument (FIG. 7) with a hex drive coupler 160 to impart additional mechanical rotational force to the outer drive sleeve 110 to assist in rod reduction.

In an example, the threaded tube 130 includes a proximal end, a distal end, a longitudinal axis extending between the proximal and distal ends, a cannulated interior, a first leg 132 and a second leg 134. The first and second legs 132, 134, in an example, are held together by the interior confines of the outer drive sleeve 110 and the retaining guide ring 120. In some examples, the first leg 132 includes an exterior threading 136A and the second leg 134 includes an exterior threading 136B. The exterior threading 136A, 136B can be a single or multi-lead thread to provide for faster reduction speed. In an example, the exterior threading 136A, 136B is a two start M18×1.5 with an effective pitch of 3 mm. In some examples, the first leg 132 includes an engagement feature 138A interior to its distal end and the second leg 134 includes an engagement feature 138B interior to its distal end. The engagement features 138A, 138B selectively engage and couple to the exterior surface of a pedicle screw assembly 150. In an example, the engagement features 138A, 138B are comprised of male protrusions that mate with female receptacles inherent on the exterior surface of the pedicle screw assembly 150. The engagement features 138A, 138B and their corresponding receptacles, in an example, provide stabilization in all three axes, as is best shown in FIG. 6A. In an example, the first leg 132 includes an exteriorly disposed feature 139A near the proximal end and the second leg 134 includes an exteriorly disposed feature 139B near the proximal end. The exteriorly disposed features 139A, 139B, in an example, are comprised of regions in which the outer diameter of the threaded tube 130 and the pitch diameter of the exterior threading 136A, 136B decrease to allow the first and second arms 132, 134 to splay open slightly at the distal end to enable easy introduction of the rod reducer 100 over the pedicle screw assembly 150 and corresponding engagement of the engagement features 138A, 138B with the receptacles of the pedicle screw assembly 150. The first and second arms 132, 134 are configured to splay open at the distal end approximately 2.5 degrees in an example.

In an example, the retaining guide ring 120 is disposed around the threaded tube 130 at the distal end of the outer drive sleeve 110 and includes first and second upwardly extending arms 122A, 122B, first and second outwardly extending tabs 124A, 124B disposed on ends of the upwardly extending arms 122A, 122B, respectively, and a rod recess 126 disposed at the distal end of the retaining guide ring 120 that selectively interfaces with the spinal rod 140.

In an example, the outer drive sleeve 110 is constructed of stainless steel, titanium, or other biocompatible surgical grade metal, while the retaining guide ring 120 and threaded tube 130 are constructed of a biocompatible polymer material such as polyetheretherketone (PEEK). However, the drive sleeve 110 is not limited to metallic constructions and the retaining guide ring 120 and the threaded tube 130 are not limited to polymeric constructions and each may be constructed of any biocompatible material that is able to take on the general shape and withstand the normal operating conditions of the components. For example, the retaining guide ring 120 and threaded tube 130 may be constructed of titanium and the drive sleeve 110 may be constructed of PEEK.

In operation, and in continuing reference to FIGS. 1-7, a pedicle screw or several pedicle screw assemblies 150 are implanted into the vertebrae of a patient and the rod 140 may be pre-bent for potential deformity correction. The spinal rod 140 is loosely placed above the construct of pedicle screws 150 and attached to the pedicle screws 150 in which no reduction is necessary. The gripping surface 112 of the outer drive sleeve 110 is engaged and rotated with respect to the threaded tube 130 using manual rotation and/or the outer drive sleeve 110 may be rotated using the ratcheting T-handle driver instrument with a hex drive coupler 160 via the drive surface 116. The retaining guide ring 120 surrounds the features 139A, 139B such that the distal ends of the first and second legs 132, 134 splay open. The distal end of the rod reducer 100 is placed over the spinal rod 140 and above a pedicle screw assembly 150 such that the first and second legs 132, 134 straddle the rod 140 and the engagement features 138A, 138B surround the corresponding receptacles on the pedicle screw assembly 150. The outer drive sleeve 110 is then rotated manually with respect to the threaded tube 130 via the gripping surface 112 and/or rotating the ratcheting T-handle driver instrument with a hex drive coupler 160 with such that the retaining guide ring 120 and the outer drive sleeve 110 travel distally with respect to the threaded tube 130 via the engagement of the interior threading 118 and the first and second exterior threading 136A, 136B, thereby causing the unsplaying of the distal ends of the first and second arms 132, 134, engagement of the first and second engagement features 138A, 138B with the receptacles on the pedicle screw 150, engagement of the rod recess 126 to the spinal rod 140, and downward translation of the spinal rod 140 with respect to the first and second legs 132, 134. A plurality of rod reducer instruments 100 can be utilized in this manner to gradually reduce the spinal rod 140 into a plurality of pedicle screw assemblies 150 over a plurality of spinal levels. The rod reducers 100, in an example, are slowly and systematically actuated to avoid overstressing the pedicle screw assemblies 150 and the interface with their corresponding vertebral bodies, which further allows for gradual stressing and stretching of soft tissue of the patient's spine while potentially correcting a deformity. The ratcheting T-handle driver instrument with a hex drive coupler 160 is then uncoupled from the outer drive sleeve 110 and locking caps, elements which serve to finally secure the spinal rod 140 with respect to the pedicle screw assemblies 150, are introduced through the rod reducers 100 via a locking cap channel provided by the interior geometry of the threaded tube 130. The locking caps can be coupled to the pedicle screw assemblies 150 using a cap driver instrument (not shown), which can be inserted through the rod reducer 100. The locking cap driver 160 has an engagement feature for coupling to the locking caps and actuating their coupling to the pedicle screw assemblies 150, such as a threaded, star drive, or hex drive engagement feature. The locking cap driver 160 may be a ratcheting driver, but is not so limited. In an example, the locking caps are coupled to the pedicle screw assemblies 150 and the locking cap driver 160 is uncoupled from the rod reducers 100. The rod reducer(s) 100 are uncoupled from the pedicle screw assemblies 150 by disposing the retaining guide ring 120 over the features 139A, 139B such that the distal ends of the arms 132, 134 are splayed open and the engagement features 138A, 138B are disengaged from their corresponding receptacles on the pedicle screw assembly(s) 150. The rod reducer 100 can be cleaned and sterilized for reuse.

In some examples, the rod reducer 100 does not introduce notches or mar the exterior of the spinal rod 140 during its reduction. In addition, the rod reducer 100 of some examples prevents splaying of the upwardly extending arms that form the rod-receiving channel of the pedicle screw assembly 150. The rod reducer 100 can be coupled to a pedicle screw assembly 150 prior to or subsequent to the implantation of the pedicle screw 150, according to surgeon preference. The rod reducer 100 can further be utilized to aid in de-rotation maneuvers of the spine during surgery.

In an example, and in reference to FIGS. 8A-8D, a rod reducer 200 is provided that is configured especially for coupling to a monoaxial pedicle screw 250 and reducing a spinal rod 140 thereto. In an example, the rod reducer 200 includes a threaded shaft 210 terminating distally in a grasping element 220 for coupling to the underside of the distal end of a monoaxial pedicle screw assembly 250. The rod reducer 200 further includes a nut 230 configured to interface with the exterior threading of the shaft 210 and threadedly translate with respect thereto. A claw element 240 having one or more arms, in an example, is coupled to the shaft 210 below the nut 230 and the one or more arms, in a further example, have a rod recess 242 for engaging the spinal rod 140.

In operation, and in continuing reference to FIGS. 8A-8D, the grasping element 220 is placed under a monoaxial pedicle screw 250. The claw element 240 engages the proximal side of the spinal rod and the nut 230 is rotated to force the claw element 240 to reduce the rod 140 via the rod recess 242 into the monoaxial pedicle screw assembly 250. A locking cap is coupled to the monoaxial pedicle screw assembly 250 and the rod reducer 200 is decoupled from the monoaxial pedicle screw assembly 250 by loosening the nut 230 and disengaging the claw 240 from the spinal rod 140.

In an example, and in reference to FIGS. 9A-9F, a rod reducer 300 is provided that includes a hex nut 310, a threaded tube 330 having a first leg 332 and a second leg 334, and a retaining guide ring 320. In an example, the rod reducer 300 is similar in function and operation to the rod reducer 100 with the exception that instead of the outer drive sleeve 110, the hex nut 310 is included and functions in conjunction with a hex socket type instrument (not shown) to actuate the rod reducer 300. The threaded tube 330 is similar in function and operation to the threaded tube 130 but incorporates a hinge design at the proximal end to control the splaying of the first and second legs 332, 334.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the present description.

The above Detailed Description includes references to the accompanying drawings, which form a part of the Detailed Description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more features thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 

What is claimed is:
 1. An apparatus configured to engage a spinal rod with an implantable screw assembly, the apparatus comprising: a spinal rod urging member that includes a bearing surface configured to selectively abut the spinal rod; and a first threaded member defining a first surface and including a first threading around at least a portion of the first surface, the first threaded member including a grasping element configured to removably couple the first threaded member to the implantable screw assembly while the implantable screw assembly is implanted into bone, wherein the first threading is configured to threadably engage a second threading of the apparatus such that relative rotation between the first threading and the second threading about an axis causes the spinal rod urging member to move along the axis with respect to the first threaded member such that the bearing surface urges the spinal rod toward the implantable screw assembly.
 2. The apparatus of claim 1, comprising a second threaded member defining a second surface and including the second threading around at least a portion of the second surface, wherein relative rotation between the first threading and the second threading about the axis causes the second threaded member to move along the axis with respect to the first threaded member.
 3. The apparatus of claim 2, wherein the spinal rod urging member is coupled to the second threaded member.
 4. The apparatus of claim 2, wherein the first surface is an outer surface and the second surface is an inner surface.
 5. The apparatus of claim 2, wherein the second threaded member includes a nut.
 6. The apparatus of claim 1, wherein the spinal rod urging member includes a claw element including one or more arms, each arm including a bearing surface configured to selectively abut the spinal rod.
 7. The apparatus of claim 6, wherein the bearing surface of each arm is disposed at an end of the arm.
 8. The apparatus of claim 6, wherein the bearing surface includes a rod recess.
 9. The apparatus of claim 1, wherein the grasping element is configured to couple to an underside of the implantable screw assembly.
 10. The apparatus of claim 9, wherein the grasping element is disposed at a distal end of the first threaded member.
 11. An apparatus configured to engage a spinal rod with an implantable screw assembly, the apparatus comprising: an engagement member including a grasping element that defines a first inner surface configured to removably couple to an underside of the implantable screw assembly while the implantable screw assembly is implanted into bone, the first inner surface facing a first direction; and a spinal rod urging member configured to couple to the engagement member, the spinal rod urging member including a second inner surface, the second inner surface facing a second direction, opposite the first direction, and configured to selectively engage the spinal rod, wherein the first inner surface is spaced from the second inner surface with respect to the second direction when the spinal rod urging member is coupled to the engagement member so as to define a gap between the first and second inner surfaces, the gap configured to receive the spinal rod along a direction that is perpendicular to a central axis of the spinal rod.
 12. The apparatus of claim 11, wherein: the engagement member defines a first curved surface and includes a first threading around at least a portion of the first curved surface; and the first threading is configured to threadably engage a second threading of the apparatus such that relative rotation between the first threading and the second threading about an axis causes the spinal rod urging member to move along the axis with respect to the engagement member such that the second inner surface urges the spinal rod toward the implantable screw assembly.
 13. The apparatus of claim 12, comprising a threaded member defining a second curved surface and including the second threading around at least a portion of the second curved surface, wherein relative rotation between the first threading and the second threading about the axis causes the threaded member to move along the axis with respect to the engagement member.
 14. The apparatus of claim 13, wherein the spinal rod urging member is coupled to the threaded member.
 15. The apparatus of claim 13, wherein the first curved surface is an outer curved surface and the second curved surface is an inner curved surface.
 16. The apparatus of claim 13, wherein the threaded member includes a nut.
 17. The apparatus of claim 12, wherein the grasping element is disposed at a distal end of the engagement member.
 18. The apparatus of claim 11, wherein the grasping element defines a recess configured to receive a shaft of a bone screw of the implantable screw assembly along a direction that is angularly offset with respect to a central axis of the shaft of the bone screw.
 19. The apparatus of claim 11, wherein the spinal rod urging member includes a claw element that defines at least one rod recess. 